Ezreal is ranged champ with quick cooldown skillshot abilities. He is also solo champion, but he can be useful at team fight especially with his ulty. There are three ways to build Ezreal: AD, AP, and hibrid. AD buld is probably best buld becouse of Ezreals attack speed witch makes this AD build pretty much DPS build and you got qoick abailities to make even more demage. and this is way I build it...

Runes for Ezreal are simple: 9 Mark of Strength (attack demage)
9 Seals of Clairty (mana regen)
9 Glyph of Focus (cooldowna reduction)
3 Quintessence of Desolation (armor pen)

Masteries are also simple 21-0-9 based on AD, armor and magic pen, cooldown reductin and mana regen.

Flash and Clairvoyance... flash i use to get into posision for my abilities also good for running away (duble flash flash + arcane shift) clairvoyance is good for his ulty, but if you dont use your ulty often of for makenig raneged kills ther rather use exhaust or ignite.

While playing at lvl 1 take Mystic Shot its Ezreal main ability, then take Arcane Shift wich is good for getting into posision for Mystic Shot. Keep taking Mystic Shot and Arcane Shift until you reach lvl 6 then you take Trueshot Barrage Ezreals ulty. Then finish Mystic Shot and Arcane Shift (each lvl 5), after you finish it keep taking Essence Flux, but on lvl 16 take again Trueshot Barrage. Just look at the picture.

I take dorans blade for start, then i go for the mana. I take boots of speed and finish manamune. Then i take sheen awsome item for ez but, before i finish trinity force i take bloodthirster (you get lifesteal form your basic demage and abilities). when you finish trinity take yoummus ghostblad for CDR and finish build with infinity edge. Some player take items for early game mid and late game. That build would look like this... EARLY GAME: dorans blade, tear of godess, boots of speed, sheen, vampiric scapter, brutalizer. MID GAME: just keep building items i go with manamune, iron boots, blood thirster and trinity. LATE GAME: finish yoummus and infinity